Composite engineered wood material piece

ABSTRACT

A composite engineered wood material piece and its method of fabrication is described. The wood material piece comprises a top wood layer secured to a substrate layer by a binder. The substrate layer has a plurality of grooves formed therein from a bottom surface thereof to enhance the flexibility of the wood material piece. The grooves are spaced from one another by one or more predetermined spaced intervals and have one or more predetermined depth and width calculated to substantially eliminate the effects of telegraphy of the grooves on a top finished surface of the top wood layer.

TECHNICAL FIELD

The present invention relates to a composite engineered wood materialpiece and its method of fabrication. The wood material piece has a topwood layer secured to a substrate layer provided with the grooves whichare sized and oriented such as to substantially eliminate the effects oftelegraphy in the top finished surface of the top wood layer.

BACKGROUND ART

It is well known in the prior art to fabricate wood boards, particularlyfor the construction of wood floors, wherein the wood boards are formedfrom solid wood or laminated wood which contains grooves in the backsurface thereof whereby to enhance the flexibility of the boards. It isalso known to fabricate wood flooring strips having small wooden slatsglued to the backside thereof at regular spaced intervals to addadditional flexibility to the floor board. The desired flexibility offloor boards is that they can conform to irregularities in the subfloorto which the boards are to be secured. Generally these floor boards areof thicknesses of ½ inch up to about 1 inch and provided with tongue andgrooves whereby to engage one another in a side-by-side and end-to-endrelationship. Such boards and the disadvantages of the related prior artare discussed for example in U.S. Pat. No. 5,283,102 issued on Feb. 1,1994.

In recent years, laminated wood boards have become thinner with the topsolid wood layer also becoming thinner normally in the range of about ⅛inch and such laminated wood boards are installed directly on a solidwood floor or on a sound absorbing material secured to the subfloor.Transverse grooves are formed in the substrate layer of these laminatedboards to provide the desired flexibility of the boards to facilitateinstallation thereof. However, because the top wood layer is relativelythin as compared to the substrate layer to which it is secured, thegrooves formed in the substrate layer become visible in the top surfaceof the top wood layer by the phenomenon of telegraphy. Accordingly, thegrooves need to be made very shallow and the top surface of the top woodlayer is preferably of light tone or provided with a non-lustre varnishin an attempt to try to conceal the appearance or reflection of thesegrooves in the top surface. Therefore, laminated products have beenconstructed with the top wood layer having a thickness ratio in therange of one-to-one with respect to the substrate and thus affecting theflexibility of the wood board and increasing the cost thereof.

SUMMARY OF THE INVENTION

It is a feature of the present invention to provide a compositeengineered wood material piece and method of fabrication whichsubstantially overcomes the above-mentioned disadvantages of telegraphy.

According to the above feature, from a broad aspect, the presentinvention provides a composite engineered wood material piece which iscomprised of a top wood layer secured to a substrate layer by bindingmeans. The substrate layer has a plurality of grooves formed thereinfrom a bottom surface thereof to enhance the flexibility of the woodmaterial piece. The grooves are spaced from one another by one or morepredetermined space distances and have one or more predetermined depthand width calculated based on parameters of the material piece tosubstantially eliminate the effects of telegraphy of the grooves on atop finished surface of the top wood layer.

According to a further broad aspect of the present invention, there isprovided a method of fabricating a composite engineered wood materialpiece having a top wood layer secured to a substrate layer by bindingmeans. The method comprises the steps of calculating from knownparameters of the top wood layer and substrate layer, the depth, widthand spacing of the grooves to be formed in a bottom surface of thesubstrate layer to enhance the flexibility of the wood material layerwhile substantially eliminating the effects of telegraphy of the grooveson a top finished surface of the top wood layer. The method furthercomprises forming a plurality of grooves in the bottom surface of thesubstrate layer having dimensions and spacing as calculated from theknown parameters.

According to a further broad aspect, the predetermined depth and widthand spacing of the grooves, in accordance with the present invention,are effected by the analysis of the following parameters: a) the type ofwood of the top wood layer, b) the intrinsic properties of the substratelayer, c) the thickness ratio between the top wood layer and thesubstrate layer, d) the top surface texture of the top wood layer, e)the properties of the binding means, and f) the type of finish coatingto be applied to a top surface of the top wood layer.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will now be describedwith reference to the accompanying drawings in which:

FIG. 1 is a fragmented perspective view of a section of a compositeengineered wood material piece constructed in accordance with thepresent invention;

FIG. 2 is a side view of an example of a composite engineered woodmaterial piece constructed in accordance with the present invention;

FIG. 3A is a perspective top view of a top wood layer to be secured to asubstrate layer and formed of oak material having a clearly defined andvisible grain surface texture;

FIG. 3B is a perspective view similar to Figure 3A but showing a topwood layer fabricated from a different type of wood, herein maple woodhaving a faint wood grain; and

FIG. 4 is a plan view of the rear surface of a composite engineered woodmaterial piece having grooves therein formed of different spacing, sizeand orientation to provide a sheet adapted to be cut to a template shapeto produce a contoured sheet having different flexible regionalcharacteristics to form a top surface of a shaped member, such as anarticle of furniture, an irregularly shaped wall surface or a multitudeof other articles.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings and more particularly to FIG. 1, there isshown generally at 10 a composite engineered wood material piece such asa floor board or slats constructed in accordance with the prior art andwhich comprises a top wood layer constructed of a superior material suchas oak, pine or maple and secured by a glue layer 12 to a substratelayer 13. Grooves 14 are formed in the substrate material 13 from abottom surface 15 thereof and at spaced intervals whereby to provideflexibility to the floor board 10. As previously described, such grooves14, through the phenomenon of telegraphy, form shaded zones 16 in thetop finished surface 17 of the top wood layer 11.

The present invention addresses this phenomenon of telegraphy andsubstantially eliminates the effects thereof on the top finished surface17. This is achieved by calculating the dimension of the depth and widthas well as the spacing of the grooves from a set of parameters of thetop wood layer and the substrate layer. These parameters include thetype of wood of the top wood layer, the intrinsic properties of thesubstrate layer, the thickness ratio between the top wood layer and thesubstrate layer, the top surface texture of the top wood layer, theproperties of the binding means and the type of finish coating to beapplied to a top surface of the top wood layer. All of these parametershave an interrelationship with respect to one another and produce theresulting telegraphy. It has been ascertained that this telegraphy iscaused by four phenomenon and namely the induced tension within thecomposite laminated material piece, the deformation of the compositematerial piece caused by deflection when it is installed on a irregularsubsurface, the change in humidity in the composite material piececausing it to expand and retract, and the dispersion or conduction ofhumidity throughout the composite wood material piece.

Because the composite engineered wood material piece of the presentinvention is comprised of two distinct laminated wood materials, namelya top wood layer 11 of wood material and a substrate layer comprised oflaminated or compressed inferior wood material glued together or othersuitable type of substrate. These glued materials will be subject totension and stress which will produce the telegraphy of the groovesformed in the bottom surface thereof. The ratio between the thickness ofthe top wood layer 11 and the substrate layer 13 is an important factorin determining the spacing 18, see FIG. 1, between the grooves 14. Ifthe ratio between the thickness of the top wood layer 11 and that of thesubstrate layer 13 is close to 1, the telegraphy of the grooves will bevery weak due to the thickness of the top wood layer 11 which is lessconductive. However, if the ration between the top wood layer and thesubstrate layer is 1:10, the telegraphy would be greatly amplified asthe top wood layer is very thin compared to the substrate layer.Accordingly, the spacing 18 between the grooves will require to becloser to one another and the dimension of the depth 19 of the groovewould have to be shorter. The width 20 of the grooves may also be madenarrower.

EXAMPLE 1

If the top wood layer 11 has a thickness of 8 mm and the substrate layer13 has a thickness of 8 mm, the telegraphy of the grooves 14 formed inthe substrate layer is nearly inexistent for the reason that thesubstrate layer cannot have much effect on the top wood layer which isof equal thickness. However, if the top wood layer is of 1 mm thicknessand the substrate layer much thicker, say 8 mm, the telegraphy of thegrooves would be very visible. Therefore, the ratio between thethickness of the top wood layer and the substrate layer is an importantfactor to consider in the determination of the configuration and spacingof the grooves.

EXAMPLE 2

Considering now two top wood layers 11, one of 2 mm and one of 4 mm,glued on a 6 mm thick substrate and with the grooves being spaced-apart2 inches and having a depth of 4 mm. The groove telegraphy in the 2 mmtop wood layer will be very visible. Accordingly, the spacing betweenthe grooves will need to be reduced to 1 inch to reduce substantiallythe telegraphy. However, for the top wood layer of 4 mm a groove spacingof 1½ inches would be sufficient to obtain an acceptable level ofreduction of the telegraphy.

Another important factor to consider is the binding material which ispreferably a glue coating applied between the top wood layer 11 and thesubstrate layer 13 with further application of pressure by means ofpresses, as is well known in the art. The adhesive material can also bepolyurethane foam or contact cement applied to opposed surfaces to bemated and let dry before the layers are contacted under pressure. Theadhesive binder or glue 12 has a predetermined elastic property andthickness and such is also a factor in the determination of thepredetermined spacing 18 of the grooves 14. Glue which is very flexiblewill permit a spacing 18 between the grooves which is larger or permit adepth of groove which is deeper as the glue acts as a relaxation zonefor the constraints of the substrate layer. The glue, or other bindingagent, could also acts as vapour barrier and reduces the transmission ofhumidity.

Another important factor taken into consideration is the depth 19 of thegrooves 14. The ratio between the depth 19 of the grooves 14 and thethickness of the substrate layer 13 has an impact on the telegraphy andthe flexibility of the wood material piece 10. For a top layer tosubstrate layer ratio of 1:8 and less, the wood material piece 10 wouldhave less flexibility and less telegraphy. Depending on the nature ofthe substrate layer, it has been ascertained that a certain flexibilitycan be achieved with a ratio of 1:3 but the telegraphy phenomenon willbe increased. In order to reduce telegraphy, the spacing 18 between thegrooves will be reduced as above-mentioned. It is pointed out that aratio of 7:8 can provoke important telegraphy in the top finishedsurface of the top layer.

The depth 19 of the grooves also has a negative effect in that itdefuses humidity within the substrate layer and can provoke increasedtelegraphy on the top surface 17 of the top wood layer 11. Although theglue layer 12 and the glue present in the substrate provide a barrier tohumidity, this barrier is broken at each groove 14. As pointed outherein above the reason for the grooves is to diminish the rigidity ofthe composite material piece or layer in order to facilitateinstallation on irregular subsurfaces.

EXAMPLE 3

With reference to FIG. 2, there is shown a specific composite engineeredwood material piece 10′ constructed in accordance with the presentinvention. The top wood layer 11 is formed of maple wood and has athickness of 4 mm. The substrate layer 13 is formed of birch wood andhas a thickness of 9 mm. If the grooves 14′ have a depth of 2 mm, thetelegraphy in the top finished surface 17 is practically invisible.However, if the grooves 14″ have a depth of 8 mm, for the same groovewidth, the telegraphy would be very visible in the top finished surface17. However, the grooves 14′ are not deep enough to provide the desiredflexibility of the composite wood material piece 10.

Another important factor taken into consideration is the composition ofthe substrate layer 13. The intrinsic properties of the substrate layer13 have an important effect on telegraphy. Substrate layers of materialall have a specific density and modulus of elasticity and hygroscopicproperties as well as other characteristics. By the formation of groovesin the substrate layer, there is created constraints in the substratelayer which are manifest on the top finished surface of the top woodlayer. A substrate material which has a high hygroscopic movement willbe, affected substantially by the formation of grooves and would have agreater impact on the appearance of the grooves on the top surface ofthe top wood layer. Accordingly, rigidity of the substrate layer affectstelegraphy. The tensions which exit in certain substrate materials dueto their lamination and the orientation of wood particles and fibres,can also provoke telegraphy when grooves are formed in such material. Asabove-described, the humidity barrier characteristic of the substrate isalso an important factor.

EXAMPLE 4

We will now consider the effects of a top wood layer 11 having athickness of 4 mm secured to two types of substrate layer 13, namely asubstrate layer constructed of MDF material and having a thickness of 8mm as compared to a substrate layer of the same thickness but fabricatedfrom plywood material. During humidity variations, the MDF substratelayer will have more important dimensional instability and will provokemore telegraphy when compared to the plywood sheet substrate which has agreater dimensional stability. Thus, the composite material which has asubstrate layer having a greater modulus of elasticity will provokeincreased telegraphy on the finished surface of the top wood layer asthere will be more deformation in the surrounding area of the grooves.

Another factor to consider in the determination of the configuration andspacing of the grooves is the top surface texture of the top wood layer.FIG. 3A shows a top wood layer formed of oak material which is a veryrigid wood material having a very high modulus of elasticity and suchwith therefore greatly reduce the telegraphy of the grooves. The oakwood has a pronounced textured grain 26 which also conceals defects inthe top finished surface 17. When the wood material pieces are used asfloor boards, one or more coats of varnish are applied to the topsurface 17 for shine and durability. It has been found that a glossysurface is more conductive of the telegraphy phenomenon that is a lessglossy surface. Also, if a stain is applied to the top surface of thetop wood layer, the darker the stain, the more visible becomes anytelegraphy and this may also be taken into consideration whencalculating the size and spacing of the groove.

EXAMPLE 5

As described above with reference to FIG. 3A and 3B, there is shown theoak material top layer 25 which is darker and provided with a pronouncedtextured grain and a maple wood top layer 27 which is lighter andcontains less grain. The maple top wood layer 27 will show moretelegraphy than the oak layer. Both top wood layers 25 and 27 have athickness of 2 mm and are secured to a same substrate layer. It has beenfound that the maple top wood layer produces a more important telegraphythan does the oak layer 25. Also, the textured grain 28 in the maplewood 27 is less pronounced and visible and therefore provides lesscamouflage to any telegraphy transmission in the wood material.

EXAMPLE 6

Considering now a top wood layer of oak material having a natural colourwith a mat finish on its top surface as opposed to a top wood layer ofmaple which is stained a dark color and provided with a high lustredfinish on its top surface. Both top wood layers are 4 mm in thicknessand are glued onto a substrate layer formed of birch and having athickness of 9 mm and grooves having a depth of 6 mm and a width of 2mm. The grooves are also spaced apart 1½ inch. When comparing bothproducts it has been found that the oak material top layer provides anadequate reduction of the telegraphy of the grooves on its top surface.Accordingly, it would be possible to utilize a glue which is lessflexible or to have the grooves spaced a greater distance apart, about1½ inches. However, with the dark stain maple wood top layer, thetelegraphy was slightly apparent. Therefore, a reduction in the spacingbetween the grooves would be necessary to greatly reduce thistelegraphy, a spacing of 1⅛ inch.

In conclusion, the finish coating applied to the top surface of the topwood layer 11 has an impact on telegraphy. A finished coating which hasless lustre will produce less telegraphy than does a high lustre surfaceas above-mentioned. However, high lustre surfaces are the preferredsurfaces of floor wood board, furniture, wall decorations, etc., andaccordingly, it is important to therefore configure the grooves such asto substantially eliminate or greatly reduce the telegraphy phenomenon.

A further factor for consideration is the determination of the width 20of the grooves 14. A very narrow groove width produces very littletelegraphy. For the laminated wood boards as above-described, it hasbeen found that a width of 1 to 2 mm provokes an average telegraphywhereas a width which is greater than 3 mm or more than 4 mm willenhance telegraphy. There is therefore a proportional relationshipbetween the transmission of telegraphy and the groove width.

As mentioned, another consideration in reducing telegraphy is thespacing 18 between the grooves. Generally speaking, a spacing of morethan 2 inches greatly increases telegraphy depending of course on thedepth and width of the grooves. A spacing of 1¼ inches or less willimprove the reduction of telegraphy and it has been found that a spacingof about one inch is more desirable as it further reduces telegraphy.However, the amount of grooves should be limited not to greatly affectthe modulus of elasticity of the substrate material.

EXAMPLE 7

For a composite material piece having a substrate layer formed of birchmaterial and of a thickness of 9 mm, and a top surface layer of maplehaving a thickness of 4 mm with a glossy surface coating, grooves havinga width of 2 mm and a depth of 6 mm would be desirable. However, withsuch a product specification, the risk of telegraphy is highly presentas we have a ratio of thickness between the top wood layer and thesubstrate layer of 4:9, a ratio of groove depth of 6:9, a rigid modulusof elasticity of the substrate, and a glossy top surface finish on themaple top wood surface. Also, any humidity will provoke deformation inthe wood material. Therefore, a spacing between the grooves of 2 incheswill make the grooves very visible on the top surface by telegraphy. Bydecreasing the spacing to about 1¼ inch, the telegraphy is practicallynon-visible and the grain in the top maple wood layer becomes morevisible due to the practically non-existing phenomenon of thetelegraphy. By reducing the spacing between the grooves to about 1 inch,the grain becomes more visible and the surface is almost unaffected bytelegraphy.

Referring now to FIG. 4, there is shown a composite engineered woodmaterial piece, herein a sheet of material, formed in accordance withthe present invention. As hereinshown, the rear surface 31 of thesubstrate layer 32 is provided with grooves oriented in groups, namelygroups 33 and 34 and wherein the orientation of the grooves 33′ of group33 and grooves 34′ of Group 34 extend at different angles whereby toprovide different zones and orientation of flexibility to the layer.Also, the grooves 34″ in group 34 are more closely spaced in a sectionof the group 34 to provide added flexibility in that section. Such anengineered composite layer may be formed for specific applications andwherein the layer may be cut to the shape of a template, such asindicated by phantom line 35, to form an overlay sheet for a repetitiveproduct, such as an article of furniture wherein the sheet is to be bentto conform to a certain shape. The spacing and dimension of the groovesis also calculated to substantially eliminate or greatly reduce thephenomenon of telegraphy. It is pointed out that the grooves can beformed by various means, such as by the use of a saw, a router bit, aslitting blade, or by spaces between glued material strips.

It is within the ambit of the present invention to cover any obviousmodifications of the preferred embodiment described herein, providedsuch modifications fall within the scope of the appended claims.

1. A composite engineered wood material piece comprising a top woodlayer secured to a substrate layer by binding means, said substratelayer having a plurality of grooves formed therein from a bottom surfacethereof to enhance the flexibility of said wood material piece, saidgrooves being spaced from one another by one or more predeterminedspaced distances, said grooves having one or more predetermined depthand width calculated based on parameters of said material piece tosubstantially eliminate the effects of telegraphy of said grooves on atop finished surface of said top wood layer.
 2. A composite engineeredwood material piece as claimed in claim 1 wherein the dimension of saidpredetermined depth and width and spacing of said grooves is determinedby the following parameters of said top wood layer and said substratelayer: i) the type of wood of said top wood layer and the intrinsicproperties of said substrate layer, ii) the thickness ratio between saidtop wood layer and said substrate layer, iii) the top surface texture ofsaid top wood layer, iv) the properties of said binding means, and v)the type of finish coating to be applied to said top surface of said topwood layer.
 3. A composite engineered wood material piece as claimed inclaim 2 wherein said substrate layer is a substrate formed from woodmaterial or other material.
 4. A composite engineered wood materialpiece as claimed in claim 3 wherein said wood material substrate isthicker than said top wood layer and constituted by one of laminatedwood, or MDF or any suitable wood substrate.
 5. A composite engineeredwood material piece as claimed in claim 2 wherein said binding means isan adhesive binder, said adhesive binder providing a humidity barrierbetween said top wood layer and said substrate layer and a flexibleinterconnection.
 6. A composite engineered wood material piece asclaimed in claim S wherein said adhesive binder is one of a glue, apolyurethane foam or a contact cement, said adhesive binder having apredetermined elastic property and thickness which constitutes one ofsaid parameters in the determination of said predetermined spaceddistances between said grooves.
 7. A composite engineered wood materialpiece as claimed in claim 2 wherein said finish coating comprises aclear protective coating having a predetermined lustre.
 8. A compositeengineered wood material piece as claimed in claim 7 wherein said finishcoating further comprises a wood stain having a predetermined tone withlighter tones being less conductive of said telegraphy.
 9. A compositeengineered wood material piece as claimed in claim 1 wherein saidgrooves are formed by one of saw grooves, routed grooves, slitting, orspaces between glued material strips.
 10. A composite engineered woodmaterial piece as claimed in claim 1 wherein said wood material piece isa floor slat or a sheet.
 11. A composite engineered wood material pieceas claimed in claim 1 wherein said grooves are formed in a rear surfaceof a composite engineered wood substrate layer, said grooves beingoriented in groups which extend at different angles whereby to providedifferent oriented zones of flexibility to said sheet.
 12. A compositeengineered wood material piece as claimed in claim 2 wherein saidcharacteristics of the intrinsic properties of said substrate layerincludes, without limitation: i) dimensional stability, ii) density ofsaid substrate material layer, and iii) the hygroscopic humidity barrierfactor.
 13. A method of fabricating a composite engineered wood materialpiece having a top wood layer secured to a substrate layer by bindingmeans, said method comprising steps of: i) calculating from knownparameters of said top wood layer and substrate layer the depth, widthand spacing of grooves to be formed in a bottom surface of saidsubstrate layer to enhance the flexibility of said wood material layerwhile substantially eliminating the effects of telegraphy of saidgrooves on a top finished surface of said top wood layer, and ii)forming a plurality of grooves in said bottom surface of said substratelayer having dimensions and spacing as calculated by step (i).
 14. Amethod as claimed in claim 13 wherein said step (i) of calculating iseffected by the analysis of the following parameters of said top woodlayer and substrate layer; i) the type of wood of said top wood layer,ii) the intrinsic properties of said substrate layer, iii) the thicknessratio between said top wood layer and said substrate layer, iv) the topsurface texture of said top wood layer, v) the properties of saidbinding means, and vi) the type of finish coating to be applied to a topsurface of said top wood layer.
 15. A method as claimed in claim 14wherein said step (ii) comprises forming said grooves by one of the useof a saw blade, a routing bit, a slitting blade, or by spaces betweenglued material strips.
 16. A method as claimed in claim 14 wherein saidcomposite engineered wood material piece is a sheet of said material,and wherein said step (i) comprises effecting said calculation forspecific portions of said sheet to determine the orientation of saidspacing as well as said depth and width of said grooves for each saidportions whereby to form said sheet with portions thereof havingdifferent oriented flexibility while substantially eliminating the saideffects of telegraphy on a top surface of said sheet.